My first experience

Hi guys,
I tried real sex for first time. But I think we overhype sex as advanced stages of meditation made me feel far better than this, even though it was my first.
So my problem goes like this, I was turned on fully with my device hard as rock, penetrated her, after 5 minutes it got soft. She aroused me again. Now here, fully aroused, I was still not able to cum. I tried again but couldn't cum. She ACTUALLY said your size is good, how come you're unable to cum. Then at the end I just masturbated myself. She told you won't cum in real sex for you've hardwired yourself this way.
Is this something incurable? Can I really cum inside someone? What should I do?